The present invention relates to information transfer between a mobile station and a radio communication network, and more particularly to a method designed to be employed in a radio communication network to obtain information from a mobile station about conditions at the mobile station during downlink transfer.
In normal wireless voice communications the telecommunication system sets up a two way communication link between a mobile station and a base station of the cellular network in which the mobile station is operating. By mobile station is meant any kind of radio communication device which operates in a cellular telecommunication system. The data stream for the voice communication is continuous and operates on a real time basis. The two way communication link consists of simultaneous transmission and reception, the base station transmits on one set of radio channels called the uplink and receives on another set of channels called the downlink. The transmit and receive channels assigned for a particular cell are separated by a fixed amount of frequency called the duplex spacing.
In addition to voice communications, digital cellular telecommunication systems increasingly support advanced high speed data services such, as short message service (SMS), broadcast paging, imaging services and fax services.
Both data and voice transmissions are improved by the emerging use of GPRS (General Packet Radio Services) protocol. GPRS provides for high speed packet radio access for GSM mobile station and routing protocols for the GSM network by the dynamic allocation of communication channels for voice and data transmissions. GPRS is defined in GSM 03.64 standard specification.
A feature of certain data services is that unlike voice transmissions, data services can be transferred unidirectionally and on a non-real time basis. For example, because paging messages can be delayed for several minutes without significant disadvantages to the receiver of the message, it allows short paging messages to be placed in a queuing system. Furthermore, the transfer of the paging message takes place in a unidirectional link from the network to the mobile station of the receiver, i.e. exclusively in a downlink transfer. When the network is transferring data in a unidirectional downlink transmission, the network must nevertheless obtain certain information from the mobile station in order to keep a check of its operation and be updated of its position in the cellular network.
One requirement is for the network to obtain information from the mobile stations on whether the downlink data which it is transmitting to the mobile station has been received. In the context of GSM, GPRS this is defined in GSM 04.60. Briefly, the approach in GPRS is to make use of a header portion of the data streamxe2x80x94the RLC/MAC (Radio Link Control/Medium Access Control) layerxe2x80x94which defines certain control criteria of the communication link.
The Medium Access Control (MAC) procedures include the functions related to the management of the common transmission resources, eg. the packet resource requests and packet resource configuration changes. The MAC procedures support the provision of Temporary Block Flows (TBFs) that allow the point-to-point transfer of signalling and user data within a cell between the network and the mobile station. Additionally, the MAC functions provide for measurement reporting for cell selection and re-selection.
The RLC function is responsible for: interface primitives allowing the transfer of Logical Link Control (LLC) layer PDU""s between the LLC layer and the MAC function; segmentation of LLC PDU""s in the RLC data blocks in reassembly of RLC data blocks into LLC/PDU, and Backward Error Correction (BER) procedures enabling the selective retransmission of RLC data blocks.
In ETSI standards MAC function is combined with RLC as one layer. RLC/MAC control blocks are used to transport RLC control messages, and only one RLC/MAC control message can be transported per RLC control block. The RLC/MAC layer comprises a series of block periods each of which is a sequence of four time slots on a packet data physical channel (PDCH) used to convey one radio block carrying one RLC/MAC protocol data unit.
Whenever the mobile station receives a RLC data block addressed to itself and with a valid RRBP (Relative Reserved Block Period) field in the RLC data block header (i.e. is polled) the mobile station transmits a packet downlink acknowledgement (ACK/NACK) message in the uplink radio block specified by the RRBP field. The acknowledgement message relates to the received downlink blocks and the quality measurement results calculated from the received blocks together with interference measurement results, and are transmitted in the uplink block based on the information in the downlink blocks (according to a certain number of bits in the downlink MAC header).
That is unless another RLC/MAC control message relating to some other information about the mobile station is waiting to be transmitted, in which case the other RLC/MAC control message is sent. However, the mobile station can only transmit an RLC/MAC control message relating to information other than packet downlink ACK/NACK at most every fourth time it is polled.
For the network to be aware of the position of the mobile station and the available options for handover the network directs a mobile station to send in measurement reports including neighbour cell information. In this context the behaviour of the mobile station is controlled by the parameter NETWORK_CONTROL_ORDER which may have the following values: NC0: xe2x80x98Normal MS Controlxe2x80x99; the mobile station does not send measurements reports and makes autonomous cell reselection, NC1: xe2x80x98Mobile Station control, with the measurement reportxe2x80x99; the mobile station sends measurement reports but makes autonomous cell reselection, NC2: xe2x80x98Network Controlxe2x80x99; the mobile station sends a measurements reports, suspend normal cell re-selection and accept network control of cell re-selection.
Accordingly, the mobile station may be directed by the network to perform neighbour cell power measurements in predefined gaps. The network indicates the location of these gaps in the packet downlink assignment message and the location and time and the size of the gaps are signalled by the following parameters: the starting time of the first TDMA frame of the first gap; a bit map indicating the time slots that are part of the gap; and the number of RLC/MAC Block periods between gaps. Once the network has signalled the gap parameters to the mobile station the network does not send an RLC/MAC block addressed to the mobile station in the time slot immediately before an assigned measurement gap, during any of the time slots of a gap or during the time slot immediately after a gap.
Neighbour cell information results are sent to the network on uplink blocks normally allocated for downlink data acknowledgement transmission. As already mentioned only a certain number of allocated uplink blocks can be used for messages other than acknowledgements and quality measurements results. In order to be able to transmit the neighbour cell measurement results as well as the required amount of acknowledgement messages, the network must send polling messages more often.
The shortest measurement period for neighbour cell re-selection measurements is 104 TDMA-frames as the maximum acknowledgement time is 64 blocks. If only one downlink time slot is allocated, the transmission of the 64 blocks last approximately 256+20 TDMA-frames (idle-frames included). Together with the fact that only every fourth of the uplink blocks allocated for the downlink ACK/NACK messages is allowed to be used for some other purposes, the neighbour message transmission with the current solution in the most stringent case will need the transmission of three extra pollings for the downlink ACK/NACK messages within every measurement period, to make it possible to send the measurement report.
Against this background the present invention aims to improve the efficiency of the use of uplink resources.
Accordingly the present invention provided a method for a radio communication network to obtain data messages from a mobile station operating therein during a unidirectional downlink transfer, the data messages being indicative of conditions at the mobile station, the method comprising the network providing a header portion of the downlink transfer having one or more unique polling codes for requesting the mobile station to transmit one or more respective data messages indicative of one or more corresponding conditions at the mobile station.
In a complementary aspect, the invention provides a radio communication system comprising a cellular network in downlink radio communication transfer with a mobile station operating therein, wherein the network provides a header portion of the transfer having one or more unique polling codes for requesting the mobile station to transmit one or more respective data messages indicative of one or more corresponding conditions at the mobile station.
By means of the invention, one or more dedicated polling messages can be transmitted for different purposes thereby separating the different cases. Thus, superfluous polling can be avoided because the messages are separated.
In a preferred embodiment, the header portion comprises the downlink RLC/MAC message header.